package md5;

public class MD5
{
  String hex_chr = "0123456789ABCDEF";

  private String rhex(int num) {
    String str = "";
    for (int j = 0; j <= 3; j++)
      str = str + this.hex_chr.charAt(num >> j * 8 + 4 & 0xF) + this.hex_chr.charAt(num >> j * 8 & 0xF);
    return str;
  }

  private int[] str2blks_MD5(String str)
  {
    int nblk = (str.length() + 8 >> 6) + 1;
    int[] blks = new int[nblk * 16];
    int i = 0;
    for (i = 0; i < nblk * 16; i++) {
      blks[i] = 0;
    }
    for (i = 0; i < str.length(); i++) {
      blks[(i >> 2)] |= str.charAt(i) << i % 4 * 8;
    }
    blks[(i >> 2)] |= 128 << i % 4 * 8;
    blks[(nblk * 16 - 2)] = (str.length() * 8);

    return blks;
  }

  private int add(int x, int y)
  {
    return (x & 0x7FFFFFFF) + (y & 0x7FFFFFFF) ^ x & 0x80000000 ^ y & 0x80000000;
  }

  private int rol(int num, int cnt)
  {
    return num << cnt | num >>> 32 - cnt;
  }

  private int cmn(int q, int a, int b, int x, int s, int t)
  {
    return add(rol(add(add(a, q), add(x, t)), s), b);
  }

  private int ff(int a, int b, int c, int d, int x, int s, int t) {
    return cmn(b & c | (b ^ 0xFFFFFFFF) & d, a, b, x, s, t);
  }

  private int gg(int a, int b, int c, int d, int x, int s, int t) {
    return cmn(b & d | c & (d ^ 0xFFFFFFFF), a, b, x, s, t);
  }

  private int hh(int a, int b, int c, int d, int x, int s, int t) {
    return cmn(b ^ c ^ d, a, b, x, s, t);
  }

  private int ii(int a, int b, int c, int d, int x, int s, int t) {
    return cmn(c ^ (b | d ^ 0xFFFFFFFF), a, b, x, s, t);
  }

  public String calcMD5(String str)
  {
    if (str == null)
    {
      return null;
    }
    int[] x = str2blks_MD5(str);
    int a = 1732584193;
    int b = -271733879;
    int c = -1732584194;
    int d = 271733878;

    for (int i = 0; i < x.length; i += 16)
    {
      int olda = a;
      int oldb = b;
      int oldc = c;
      int oldd = d;

      a = ff(a, b, c, d, x[(i + 0)], 7, -680876936);
      d = ff(d, a, b, c, x[(i + 1)], 12, -389564586);
      c = ff(c, d, a, b, x[(i + 2)], 17, 606105819);
      b = ff(b, c, d, a, x[(i + 3)], 22, -1044525330);
      a = ff(a, b, c, d, x[(i + 4)], 7, -176418897);
      d = ff(d, a, b, c, x[(i + 5)], 12, 1200080426);
      c = ff(c, d, a, b, x[(i + 6)], 17, -1473231341);
      b = ff(b, c, d, a, x[(i + 7)], 22, -45705983);
      a = ff(a, b, c, d, x[(i + 8)], 7, 1770035416);
      d = ff(d, a, b, c, x[(i + 9)], 12, -1958414417);
      c = ff(c, d, a, b, x[(i + 10)], 17, -42063);
      b = ff(b, c, d, a, x[(i + 11)], 22, -1990404162);
      a = ff(a, b, c, d, x[(i + 12)], 7, 1804603682);
      d = ff(d, a, b, c, x[(i + 13)], 12, -40341101);
      c = ff(c, d, a, b, x[(i + 14)], 17, -1502002290);
      b = ff(b, c, d, a, x[(i + 15)], 22, 1236535329);

      a = gg(a, b, c, d, x[(i + 1)], 5, -165796510);
      d = gg(d, a, b, c, x[(i + 6)], 9, -1069501632);
      c = gg(c, d, a, b, x[(i + 11)], 14, 643717713);
      b = gg(b, c, d, a, x[(i + 0)], 20, -373897302);
      a = gg(a, b, c, d, x[(i + 5)], 5, -701558691);
      d = gg(d, a, b, c, x[(i + 10)], 9, 38016083);
      c = gg(c, d, a, b, x[(i + 15)], 14, -660478335);
      b = gg(b, c, d, a, x[(i + 4)], 20, -405537848);
      a = gg(a, b, c, d, x[(i + 9)], 5, 568446438);
      d = gg(d, a, b, c, x[(i + 14)], 9, -1019803690);
      c = gg(c, d, a, b, x[(i + 3)], 14, -187363961);
      b = gg(b, c, d, a, x[(i + 8)], 20, 1163531501);
      a = gg(a, b, c, d, x[(i + 13)], 5, -1444681467);
      d = gg(d, a, b, c, x[(i + 2)], 9, -51403784);
      c = gg(c, d, a, b, x[(i + 7)], 14, 1735328473);
      b = gg(b, c, d, a, x[(i + 12)], 20, -1926607734);

      a = hh(a, b, c, d, x[(i + 5)], 4, -378558);
      d = hh(d, a, b, c, x[(i + 8)], 11, -2022574463);
      c = hh(c, d, a, b, x[(i + 11)], 16, 1839030562);
      b = hh(b, c, d, a, x[(i + 14)], 23, -35309556);
      a = hh(a, b, c, d, x[(i + 1)], 4, -1530992060);
      d = hh(d, a, b, c, x[(i + 4)], 11, 1272893353);
      c = hh(c, d, a, b, x[(i + 7)], 16, -155497632);
      b = hh(b, c, d, a, x[(i + 10)], 23, -1094730640);
      a = hh(a, b, c, d, x[(i + 13)], 4, 681279174);
      d = hh(d, a, b, c, x[(i + 0)], 11, -358537222);
      c = hh(c, d, a, b, x[(i + 3)], 16, -722521979);
      b = hh(b, c, d, a, x[(i + 6)], 23, 76029189);
      a = hh(a, b, c, d, x[(i + 9)], 4, -640364487);
      d = hh(d, a, b, c, x[(i + 12)], 11, -421815835);
      c = hh(c, d, a, b, x[(i + 15)], 16, 530742520);
      b = hh(b, c, d, a, x[(i + 2)], 23, -995338651);

      a = ii(a, b, c, d, x[(i + 0)], 6, -198630844);
      d = ii(d, a, b, c, x[(i + 7)], 10, 1126891415);
      c = ii(c, d, a, b, x[(i + 14)], 15, -1416354905);
      b = ii(b, c, d, a, x[(i + 5)], 21, -57434055);
      a = ii(a, b, c, d, x[(i + 12)], 6, 1700485571);
      d = ii(d, a, b, c, x[(i + 3)], 10, -1894986606);
      c = ii(c, d, a, b, x[(i + 10)], 15, -1051523);
      b = ii(b, c, d, a, x[(i + 1)], 21, -2054922799);
      a = ii(a, b, c, d, x[(i + 8)], 6, 1873313359);
      d = ii(d, a, b, c, x[(i + 15)], 10, -30611744);
      c = ii(c, d, a, b, x[(i + 6)], 15, -1560198380);
      b = ii(b, c, d, a, x[(i + 13)], 21, 1309151649);
      a = ii(a, b, c, d, x[(i + 4)], 6, -145523070);
      d = ii(d, a, b, c, x[(i + 11)], 10, -1120210379);
      c = ii(c, d, a, b, x[(i + 2)], 15, 718787259);
      b = ii(b, c, d, a, x[(i + 9)], 21, -343485551);

      a = add(a, olda);
      b = add(b, oldb);
      c = add(c, oldc);
      d = add(d, oldd);
    }
    return rhex(a) + rhex(b) + rhex(c) + rhex(d);
  }
}